Slim profile indicating instruments

ABSTRACT

The present invention concerns the structure of and methods of constructing indicating instruments with slim profiles. The indicating instrument comprises a meter movement and a circuit board. The main body of the meter movement is situated in an aperture in the circuit board. With this placement, the front end of the body of the meter movement extends a distance in front of the circuit board and the back end of the meter movement body extends a distance behind the circuit board. Through appropriate selection and arrangement of any components on the circuit board, the circuit board can be constructed such that none of its components extend beyond the distance that the meter movement extends on either side of the circuit board. In this manner the space needed for the meter movement and the circuit board and its components collapses into the same area. A light plate may be added to the circuit board and meter movement. The light plate provides a structural framework for the indicating instrument. The circuit board and meter movement may be mounted to the light plate. In this manner, the internal components of the indicating instrument are all held together and can be calibrated and tested without the addition of any further components.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 09/912,196entitled “Slim Profile Indicating Instruments”, filed 23 Jul. 2001, nowU.S. Pat. No. 6,701,718 which claimed the benefit of U.S. provisionalapplication No. 60/220,456 entitled “Slim Profile Tachometer,” filed on24 Jul. 2000. Each of the above-referenced applications is herebyincorporated by reference as though fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an indicating instrument assembly of any typeand more directly to an assembly structure that decreases the depthrequired for the instrument assembly.

2. Description of the Related Art

Indicating instruments are used for numerous applications across avariety of industries and within innumerable types of machines, systems,and vehicles. Indicating instruments can, for example, measure the speedof a vehicle, such as an automobile or airplane, or measure therotational speed of an engine shaft or turbine to indicate a need toswitch to an appropriate gear ratio so that the motor is not overworked.Indicating instruments can also be fuel, pressure, and temperaturegauges, which are found, for example, on vehicles, heavy equipment,assembly line apparatuses, and other industrial equipment. Complexvehicles and other equipment may have a variety of other special purposeindicating instruments to measure any recordable or gaugable activity orcondition. For example, airplanes and submarines may have altitude anddepth gauges, respectively.

In many situations it is desirable to construct an indicating instrumentas small as possible because of size constraints of the environment inwhich it is used. For example, in an airplane cockpit a large number ofinstruments must be placed in an extremely limited area. The size of theindicating instrument is considered not only as a factor of its exposedsurface area as viewed by an operator, but also in terms of the amountof space taken, for example, under a mounting surface or behind a panel,by the instrument's functional and mounting components.

In other instances, it is desirable that the exposed portion of theindicating instrument be quite large so that the operator can easilyperceive the presentation of the gauged information. In thesesituations, although it may be desirable to provide a large display forthe information, it may be equally desirable that the indicatinginstrument be otherwise small in size due to similar constraints ofspace for housing or mounting the underlying functional components. Anexample of these competing needs may be seen in the dashboardinstruments of an automobile such as speedometers and tachometers wherethe dial size is desired to be large for easy reading, but the mountingand housing space within the dashboard is limited.

Indicating instruments may also be manufactured for sale on the“aftermarket,” wherein additional instruments or devices, which wereunavailable as options on the vehicle or other equipment at the time oforiginal purchase, are provided for installation by the operator. In thecase of aftermarket indicating instruments such as speedometers ortachometers, these gauges may be provided for mounting on top of thedashboard or at another location in the vehicle for ease of viewing bythe operator. For example, many aftermarket tachometers are sold toautomobile operators involved in stock car racing. In such racing it isimportant for the operator to know when to shift, but it is imperativethat the operator be able to concentrate on the raceway and thecompetitor vehicles in order to avoid a collision. Many of these racingoperators prefer to mount an aftermarket tachometer on top of thedashboard, or otherwise in the area of the windshield, so they do nothave to lower their eyes from the road to read an original equipmenttachometer mounted within the dashboard.

Prior art indicating instruments 200, such as those shown in FIGS. 1A,1B, 2A, and 2B, depict aftermarket tachometers with their own housingsfor dashboard mounting applications. Because of standard designconfigurations, these indicating instruments 200 are relatively deep inbody thickness from the face of the instrument to the back of thehousing. The thickness of these instruments 200 is dictated in largepart by the size of the meter movement 210, the rear end of which isgenerally mounted to a printed circuit board (PCB) 230. The metermovement 210 and PCB 230 assembly is then mounted to and within thehousing 240 of the indicating instrument 200, generally by mountingscrews 220 a and 220 b, to provide a firm support for the meter movement210, PCB 230, and related display components of the indicatinginstrument.

The indicating instrument of FIG. 2B is configured with dual PCBs 230and 230′, which further increases the necessary depth of the housing toenclose the additional PCB components. Generally a gap is also neededbetween the PCB 230′ and the rear of the housing 240 in order to allowroom for the circuit components mounted on and extending from the PCB230′, again deepening the housing. The design of mounting screws 220 aand 220 b, which extend beyond the housing in FIG. 2B, further increasethe overall depth of the indicating instrument.

In aftermarket applications, such significant depth of an indicatinginstrument can make it difficult to fit and install on the dashboard ofa vehicle, especially in the case of a narrow dashboard or a steepwindshield slope. In applications where the indicating instrument isintegrated into the original design of the vehicle, machine, or othersystem control, the prior art designs of indicating instruments requirerelatively deep spaces to house their functional components.

SUMMARY OF THE INVENTION

The present invention concerns the structure of and methods ofconstructing indicating instruments with slim profiles. What is meant by“slim profile” is that indicating instruments according to thisinvention are of shallow depth or are relatively thin between the faceof the indicating instrument and the rear most component or the backpanel of any housing enclosing the indicating instrument.

At a base level, an indicating instrument according to this inventionmay comprise a meter movement and a circuit board. In order to achievethe slim profile, the main body of the meter movement is situated in anaperture in the circuit board. With this placement, the front end of thebody of the meter movement extends a distance in front of the circuitboard and the back end of the meter movement body extends a distancebehind the circuit board. Through appropriate selection and arrangementof any components on the circuit board, the circuit board can beconstructed such that none of its components extend beyond the distancethat the meter movement extends on either side of the circuit board. Inthis manner the space needed for the meter movement and the circuitboard and its components collapses into the same area.

In a further embodiment, a light plate may be added to the circuit boardand meter movement. The light plate may be seen as a structuralframework for the indicating instrument. The light plate is a rigid,refractive material, and in one embodiment is a molded plastic platewith boss mounts and boss extensions molded as protrusions from the backside of the light plate. The circuit board is mounted to the boss mountsextending from the light plate. In this way, the boss mounts provideappropriate spacing between the light plate and the circuit board toallow room for the front end of the main body of the meter movement andany components of the circuit board to reside. The meter movement mayalso be mounted to the back side of the light plate to provide securepositioning of the meter movement relative to the rest of the componentsof the indicating instrument. In this manner, the internal components ofthe indicating instrument are all held together and can be calibratedand tested without the addition of any further components. This providesa benefit in that significant disassembly is avoided in the event that afunctional component is bad and needs to be replaced.

In an alternative embodiment, the indicating instrument may have asecond circuit board. This second circuit board may be positionedbetween the light plate and the first circuit board and similarlymounted to boss mounts extending from the light plate. In oneembodiment, the terminals of the meter movement may be directlyelectrically and mechanically attached to the second circuit board.

Aside from its structural function in this invention, the purpose of thelight plate is to transmit light from a light source to the face of anindicating instrument to illuminate the dial. In an embodiment of thepresent invention the light plate collects light from a light source,for example, a light bulb mounted on the circuit board, via a projectionfrom the back side of the light plate that contains an aperture. Theaperture is large enough to surround the light bulb projecting from thecircuit board. In this manner, the light bulb need take up no more spacethan the gap provided between the light plate and the circuit board bythe boss mounts and taken up by the meter movement and other circuitboard components. The edges of the aperture in the light platesurrounding the light bulb collect the emitted light and transmit itthrough the light plate to its edge around the dial on the face of theindicating instrument where the light is emitted from the light plate.

The indicating instrument may further have a pointer that travels overthe dial face. The pointer may be attached to a shaft extending from themeter movement through apertures in the light plate and dial face. Thepointer may move in a plane above and parallel to the dial face andunderneath a lens. The pointer may be halted in its travel by a pointerstop protruding from the dial face. In one embodiment, the pointer stopis a light emitting diode (LED) that further functions as an indicatorof a condition of the indicating instrument. The LED is electrically andmechanically connected to the circuit board and protrudes throughapertures in the light plate and dial face. The pointer stop extendsabove the dial face far enough to intersect the sweep of the pointer andstop the movement of the pointer.

The various components of the indicating instrument may be contained ina housing for protection or for individually mounting the indicatinginstrument, for example, external to an instrument panel integrated intothe machinery for which the indicating instrument is providingmeasurements. The housing may cover the back of the indicatinginstrument components and be fitted with a lens through which the faceof the indicating instrument may be viewed. In one embodiment, the lensis attached to the housing by a bezel surrounding circumferential edgesof the lens and housing, clamping the two together. A gasket may beplaced between the lens and both the housing and the edge of the lightplate as a cushion and a seal. Also, in one embodiment, the housing maybe formed with a circumferential ledge normal to the side wall. The bossextension of the light plate may extend beyond the edges of the circuitboard to make contact with the ledge. Due to the clamping pressure ofthe bezel transferred through the lens and the gasket to the light plat,the light plate, supported by the boss extension, is held firmly againstthe housing ledge.

In another embodiment of the invention, the lens of the indicatinginstrument is constructed with a concentric projection around the edgeof the face. This projection supports the bezel and prevents the edge ofthe bezel from scratching or otherwise damaging, for example, gouging orcracking, the optical surface of the lens. In yet another embodiment ofthe indicating instrument, the concentric projection of the lens mayfurther be a channel bounded by two walls. Either the first wall or thesecond wall may provide the support to the bezel. In addition, the lensmay have a concentric projection around the edge of the lens oppositethe channel. With this lens construction, it is possible to place a lenson a relatively flat surface without scratching the optical surface ofthe lens. It is further possible to stack lenses on top of each other,for example, during shipping of lenses as individual components, withthe projection of the second side fitting into the channel of the firstside. In this way, the optical surfaces of the lenses are separated fromeach other and the lenses are unable to rub against each other, therebypreventing scratching and other damage.

An indicating instrument with a housing may be mounted on varioussurfaces and in various configurations through the use of a mountingstrap that surrounds the housing. The mounting strap can be tightened orloosened around the housing through the use of a tightening means. Theindicating instrument may be rotated within the mounting strap andsecured at any position by tightening the tightening means. In oneembodiment, the tightening means may be a bolt with a nut that connectstwo ends of the mounting strap and draws them toward each other, therebytightening the mounting strap around the housing. Also attached to themounting strap may be a mounting foot, which can be attached to varioussurfaces at various angles. In one embodiment the mounting foot can besecured into a particular position by tightening the tightening means.In the particular embodiment wherein the tightening means is a bolt, themounting foot may similarly be held to the mounting strap by the boltand secured when the nut is tightened.

The indicating instrument may further have an external indicator toindicate a condition of the indicating instrument. This may be the samecondition or a different condition than the condition indicated by thepointer stop indicator in the embodiment previously described. Theexternal indicator may have a mounting foot that can be held between themounting strap and the housing of the indicating instrument, wherein themounting foot is attached to the indicating instrument. In anotherembodiment, the external indicator can be mounted at a location separatefrom the indicating instrument, but maintain communication with theindicating instrument, for example, by wires.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of the face of a prior art indicating instrument.

FIG. 1B is a cross-sectional view of the prior art indicating instrumentof FIG. 1A from the right side.

FIG. 2A is a plan view of the face of a second prior art indicatinginstrument.

FIG. 2B is a cross-sectional view of the prior art indicating instrumentof FIG. 2B seen from the right side showing the use of two circuitboards.

FIG. 3A is a plan view of the face of an embodiment of an indicatinginstrument according to the present invention.

FIG. 3B is a plan view of the right side of the indicating instrument ofFIG. 3A.

FIG. 4A is a plan view of the face of an embodiment of an indicatinginstrument according to the present invention.

FIG. 4B is a cross-sectional view of the indicating instrument of FIG.4A taken along line 4B—4B.

FIG. 5 is an exploded isometric view of the construction of the face andcircuit board assembly of an embodiment of an indicating instrumentaccording to the present invention.

FIG. 6 is an exploded isometric view of the components of an embodimentof an indicating instrument according to the present invention.

FIG. 7A is a plan view of the front side of a circuit board of anembodiment of an indicating instrument according to the presentinvention.

FIG. 7B is a plan view of the back side of the circuit board of FIG. 7A.

FIG. 8 is a cross-sectional view of an embodiment of an indicatinginstrument utilizing two circuit boards according to the presentinvention.

FIG. 9A is a plan view of the end of a switch shaft component used withan embodiment of an indicating instrument according to the presentinvention.

FIG. 9B is a first plan view of a portion of the surface along thelength of a switch shaft component used with an embodiment of anindicating instrument according to the present invention.

FIG. 9C is a second plan view of a portion of the surface of a switchshaft component used with an embodiment of an indicating instrumentaccording to the present invention.

FIG. 9D is a cross-sectional view of a knob for a switch shaft componentused with an embodiment of an indicating instrument according to thepresent invention.

FIG. 9E is a plan view of the bottom of the knob of FIG. 9D.

FIG. 9F is a fragmentary view, partially in cross-section, of anembodiment of an indicating instrument according the present inventiondetailing the placement of a switch.

FIG. 10A is a plan view of the front of a pointer used in an embodimentof an indicating instrument according to the present invention.

FIG. 10B is a partial cross-sectional view of the right side of thepointer of FIG. 10A.

FIG. 11 is a partial view in cross-section of stacked lenses used in anembodiment of an indicating instrument according to the presentinvention.

FIG. 12 is a partial view in cross-section of the assembly of the faceof an embodiment of an indicating instrument according to the presentinvention.

FIG. 13A is a plan view of a reflector, prior to assembly, for use in anexternal indicator of an embodiment of an indicating instrument of thepresent invention.

FIG. 13B is an isometric view of the reflector of FIG. 13A assembled.

FIG. 14A is a cross-sectional view of a first configuration of a strap,strap pad, and housing in an embodiment of an indicating instrumentaccording to the present invention.

FIG. 14B is a cross-sectional view of a second configuration of a strap,strap pad, and housing in an embodiment of an indicating instrumentaccording to the present invention.

FIG. 15 is a plan view of the right side of an embodiment of anindicating instrument according to the present invention, wherein theexternal indicator is mounted on a surface apart from the body of theindicating instrument.

FIG. 16 is a plan view of the back of an embodiment of an indicatinginstrument according to the present invention with an access plugremoved.

FIG. 17 is a plan view of the back of the indicating instrument of FIG.16 with the access plug in place.

FIG. 18 is a plan view of the back of an embodiment of an indicatinginstrument according to the present invention with an alternate wiringand access scheme.

FIG. 19 is a plan view of the right side of an embodiment of anindicating instrument according to the present invention with analternate configuration of the external indicator and the strap pad.

FIGS. 20A and 20B are plan views of the right side of an embodiment ofan indicating instrument according to the present invention in alternateupside down mounting positions with the mounting foot reversed.

FIGS. 20C and 20D are plan views of the right side of an embodiment ofan indicating instrument according to the present invention in alternateupside down mounting positions with the mounting foot facing forward.

FIGS. 20E, 20F, and 20G are plan views of the right side of anembodiment of an indicating instrument according to the presentinvention in alternate mounting positions with the mounting foot facingforward.

FIGS. 20H and 20I are plan views of the right side of an embodiment ofan indicating instrument according to the present invention in alternatemounting positions with the mounting foot reversed.

FIG. 20J is a plan view of the bottom of an embodiment of an indicatinginstrument according to the present invention, turned on its right side.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of providing a detailed description of an indicatinginstrument according to the present invention, an aftermarket automobiletachometer has been chosen as an exemplary embodiment for describing thenovel features of the invention. The inventive design as translated inthe tachometer is merely one representation of the application of thenovel construction techniques for indicating instruments disclosedherein, which are equally applicable to indicating instruments of alltypes. The tachometer is chosen because of the ease of describing thenovel construction techniques as applied to this particular indicatinginstrument. In addition, an aftermarket embodiment is chosen as a meansof detailing a complete set of features (for example, an instrumentincluding a housing), many of which would be inapplicable to anindicating instrument for an integrated application, such as ifincorporated into an automobile dashboard display.

FIG. 3A shows the face 3 of an indicating instrument 1 (a tachometer) ofthe novel configuration disclosed herein. Primary elements of theindicating instrument seen in this view include: a housing 2 (FIG. 3B);a bezel 4 that attaches a lens 6 to the housing 2; a gasket 8 to cushionthe lens 6 and separate it from a light plate 10 (FIG. 4B) and a dialface 14, which is seen through the lens 6 and is printed with theinstrument markings; and a pointer 16 with a pointer cap 20, the pointer16 indicating the instrument reading against the markings on the dialface 14. For an aftermarket automotive application, the face 3 may be ofa large diameter for ease of reading by the vehicle operator. While theface 3 may be sizable, the depth of the indicating instrument 1, asviewed from the side in FIG. 3B, is substantially less than the typicalprior art indicating instruments depicted in FIGS. 1B and 2B. The slimprofile of the indicating instrument 1 is achieved through the novelcomponent designs and mounting configurations of the present invention.

FIG. 4B depicts a cross-sectional view of the indicating instrument 1,wherein the cut-away of the section presented is indicated by the brokenline 4B—4B across the face 3 of the indicating instrument 1 in FIG. 4Aand the direction of the view is indicated by the arrows on the ends ofline 4B—4B. Other views that may aid the reader with reference to thefollowing discussion may be found in FIGS. 5, 6, 7A, and 7B. As isreadily seen, while the face 3 of the indicating instrument 1 is quitelarge for ease of viewing, the housing 2 containing the components ofthe indicating instrument 1, in contrast, defines a very slim profile. Asignificant space savings is achieved through novel designs andarrangements of the components within the housing of the indicatinginstrument 1.

The most significant space saving design feature is an aperture createdin the printed circuit board (PCB) 70, the PCB hole 72, through whichthe meter movement 52 is placed, rather than mounting the meter movement52 behind the surface of the PCB 70 as in prior art designs. The metermovement 52 translates electrical impulses into rotational movement tomove the pointer 16 around the dial face 14. By placing the metermovement 52 so that it extends through the plane of the PCB 70, aslimmer profile housing 2 can be used. The circuit components 134 (FIGS.7A and 7B) on each side of the PCB 70 may be chosen to extend no morethan the thickness of the meter movement 52 protruding from either sideof the PCB 70, thereby combining two depth intensive components in thesame space.

A second embodiment of an indicating instrument 1 according to thepresent invention is shown in FIG. 8. In this instance, the diameter ofthe indicating instrument 1 is required to be smaller, for examplebecause of space constraints on the area allotted to the size of theface 3 in an instrument collection. It is often the case that a secondPCB 71 is then needed to accommodate all the circuit components that canno longer fit on a single, smaller-diameter PCB 70′. The concept ofproviding a hole in the PCB 70′ to encompass a component (e.g. the metermovement 52) can be expanded to the second PCB 71 to achieve a slimprofile indicating instrument 1, even with a decreased diameter. Themeter movement 52 may be mounted so that it extends through a hole inthe plane of the first PCB 70′ and the second PCB 71 may be mounted infront of meter movement 52, between the meter movement 52 and the lightplate 10.

The second PCB 71 may have multiple apertures for accommodating variouscomponents in the indicating instrument 1. For example, in the secondembodiment depicted in FIG. 8, the second PCB 71 has a light plate hole73 a for accepting the extension of the light plate 10 that encirclesthe lamp 54 to collect the emitted light; a shaft hole 73 b throughwhich the shaft 106 extending from the meter movement 52 extends toconnect with the pointer 16; one or more boss mount holes 73 c allowingthe boss mounts 12 to attach to the first PCB 70, and a pot extensionhold 73 d and a switch extension hole 73 e through which the pot shaftextension 24 and switch shaft extension 30, respectively, may extend toprotrude above the face 3 of the indicating instrument 1. The second PCB71 is held in radial alignment by the protrusion of these variouscomponents through these various holes. The second PCB 71 is held inaxial alignment by the direct connection of the terminals 53 a, 53 b(not shown in FIG. 8), and 53 c of the meter movement 52 to the PCB 71.(In the embodiment of FIG. 7A, the terminals 53 a–c of the metermovement 52 are connected to the PCB 70 by meter movement leads 114a–c.) Through this novel configuration of the PCBs 70′, 71, the axiallength needed for the housing 2 covering the components of theindicating instrument 1 is minimized. In fact, the additional axiallength needed may be as little as the thickness of the second PCB 71.

As seen in prior art FIGS. 1B and 2B, the common internal mountingstructure in the prior art indicating instruments 200 is through the useof long bolts 220 a–b and spacers 225 a–b that thread through the PCB230 and the housing 240, thereby attaching the components to the housing240. The use of these bolts 220 a–b additionally increases the thicknessof the prior art indicating instruments 200 because of the bolt headsand nuts needed to fasten the bolts 220 a–b in place.

A second, novel, space-saving technique of the present invention is theuse of a light plate 10 as the principle mounting structure in theindicating instrument 1, as seen in FIG. 4B. Light transmission based onlight pipe technology (the use of internally refractive compositematerials that can reflect light to travel throughout the materials'structure) is commonly used in indicating instrument construction. Lightpipes of various configurations are used in the prior art to transmitlight from a light source to illuminate the face of an indicatinginstrument. In an embodiment of the present invention, light pipematerial is fabricated into a generally disk-shaped light plate 10. Thecircumferential edges of the light plate 10 are beveled to reflectlight, originating from behind the dial face 14, across the face 3 ofthe indicating instrument 1. Lamp 54 interfaces with lamp socket 56,which is mechanically and electrically connected with PCB 70 throughsocket aperture 108, thereby holding the lamp 54 in proper position andproviding electrical power to illuminate the lamp 54. The lamp 54 ispositioned within a aperture 110 protruding from the rear of the lightplate 10, whereby the edges of the light plate 10 surrounding theprotruding aperture 110 collect the emitted light from lamp 54 anddirect it to the face 3 of the indicating instrument 1.

In addition to transmitting light to the dial 14, this invention furtherutilizes the light plate 10 as a mechanical framework to mountcomponents, align parts, and facilitate the manufacture and functioningof the indicating instrument 1. To achieve the benefits of a slimprofile for the indicating instrument 1, the light plate 10 may befabricated to include additional structures such as boss mounts 12 andboss extensions 32. The boss mounts 12 may be generally cylindricalappendages with either threaded molded holes or self tapping aperturesfor receiving mounting screws. The boss mounts 12 extend from the rearof the light plate 10 to create a gap between the light plate and PCB70. The PCB 70 is attached to the boss mounts 12 with mounting screws 62through mounting screw apertures 118 a–d (FIG. 6). The gap between thelight plate 10 and PCB 70 is sized to allow sufficient room for circuitcomponents 134 (FIGS. 7A and 7B) on the PCB 70, the extension of themeter movement 52 through the PCB 70, and other features to be describedherein.

The boss extensions 32 in the described embodiment may be smaller,shorter extensions from the light plate 10 that are sized to space thelight plate 10 away from a ledge 33 in the wall of the housing 2. Theboss extensions 32 provide firm axial alignment of the light plate 10against the housing 2 and thereby prevent axial movement of the PCB 70,of the meter movement 52, and of other components affixed to the lightplate 10 within the housing 2. The measurements of the boss mounts 12,boss extensions 32, and housing ledge 33 are all chosen in relation toeach other to provide appropriate spacing between components, whilestill achieving a slim profile for the indicating instrument 1.

The light plate 10 further supports and provides a mounting surface forthe dial face 14 and the meter movement 52. The dial face 14 is situateddirectly upon a flat surface of the light plate 10. Meter movementmounts 112 a–b (FIG. 6) extend from the meter movement 52 and areattached to the light plate 10 with dial face screws 76 a–b. The dialface screws 76 a–b also secure the dial face 14 to the light plate 10and further act to align the dial face with reference to the otherfunctional and display components on the face 3 of the indicatinginstrument 1. In this way, the light plate 10 acts as a framework tohold all functional parts as one assembly. This allows completecalibration and testing of the functional components of an indicatinginstrument 1 before installing the functional components in the housing2 or other environment and attaching any associated peripheral parts.The ability to test the functionality of an indicating instrument 1before it is encompassed in a housing 2 is a great benefit tomanufacturing economy, as malfunctioning components can easily bereplaced without having to take apart the entire indicating instrument1.

Another function of the light plate 10 is to provide radial and axialalignment of the components with respect to the housing 2. Radialalignment is provided by the abutment of the exterior circumference ofthe light plate 10 with the internal wall 74 of the housing 2. In thisexemplary embodiment, PCB 70 also has alignment notches 137 a–b (FIG. 5)that mate with housing indentions 136 a–b (FIG. 6) in housing 2providing additional radial alignment and preventing rotational movementaround a center axis A. Since the PCB 70 is attached to the light plate10, the conjunction of the alignment notches 137 a–b and the housingindentions 136 a–b provide radial stability to all the components of theindicating instrument 1. Other means of radial alignment of componentsthrough an interface with the housing 2 are well known in the art. Axialalignment is provided by the contact between the boss extensions 32 andthe housing ledge 33 as described above. Axial alignment may also beaugmented by dimple 34 in the rear of the housing 2, which limits anymovement of the meter movement 52 in the housing 2.

The light plate 10 also receives holding pressure from the face 3 of theindicating instrument 1, thereby further preventing axial rotation, bythe combination of the lens 6 and a gasket 8. The gasket 8 may berubber, or other similar elastic but minimally compressive material,that provides spacing between the dial face 14 on the light plate 10 andthe lens 6 to allow room for the pointer 16 to sweep the dial face 14.The lens 6 is placed opposite the light plate 10, sandwiching the gasket8 in between. The lens 6 is held against the gasket 8 by a bezel 4,which clamps around the circumference of the face 3 of the indicatinginstrument 1, clasping the lens 6 along one edge of the bezel 4 and thehousing 2 along a second edge of the bezel 4. The combination of thelens 6, gasket 8, light plate 10, bezel 4, and housing 2 fixes theentire internal assembly of the indicating instrument 1 in place.

Additional projections from the light plate 10, extending in thedirection of the face 3 and identified as pot tube 66 and switch tube68, also prevent rotation of the various components relative to eachother. Pot tube 66 and switch tube 68 may be of unitary constructionwith the light plate 10 and extend though apertures in the dial face 14and lens 6, positively aligning the dial face 14 and the lens 6. The pottube 66 and switch tube 68 also provide good bearing surfaces for potshaft extension 24 and switch extension 30, which are further describedlater herein.

A design feature may be added to the pot tube 66 and switch tube 68 tocontrol unwanted light transmitted through the pot tube 66 and switchtube 68 as they are integral to the light plate 10. This escaping lightis prevented by forming the ends of the pot tube 66 and switch tube 68projections as conical surfaces 69 (of approximately 45° angles). SeeFIG. 9F. The conical surfaces refract the light harmlessly inward towardthe pot shaft extension 24 and the switch shaft extension 30. Also,opaque tubing 64 a–b may be placed over the pot tube 66 and switch tube68 projections between the dial face 14 and the lens 6 to containunwanted light.

It is preferred that lens 6 have smooth polished surfaces with opticalclarity. However, this is not a requirement for the functionality of theinvention. Prior art indicating instrument 200 lenses 250, seen in FIGS.1B and 2B are typically made as flat disks. The lens surfaces are verysensitive to scratching that can result if lenses are allowed to moveand touch each other, which is usually the case as prior art lenses arestacked for shipping or for availability during the assembly of theindicating instruments 200. This can be a very serious problem, whichoften demands careful individual wrapping of individual lenses forstorage and handling before assembly into the indicating instruments200. The present invention solves the problem of scratched lenses 6 byforming a concentric channel 5 and a concentric projection 7 around thecircumference of each lens 6, as shown to best advantage in FIG. 11. Theconcentric projection 7 of a first lens 6 can rest in the concentricchannel 5 of a second lens 6, thereby interlocking in such a way as toprovide good separation and to prevent radial movement between each lens6 when stacked for shipping or use in assembly of indicating instruments1. Thus the surfaces of lenses 6 are well protected for bulk handling.

The lens 6 may also be protected from the sharp edge of the bezel 4 uponassembly to prevent damage to the lens 6. Prior art indicatinginstruments 200, as seen in FIGS. 1B and 2B, typically add a spacer 260between the bezel 270 and lens 250. The present invention provides for aproper spacing between the sharp edge of the bezel 4 and the opticalsurface of the lens 6 as shown in FIG. 12. By spacing the walls formingthe concentric channel 5 to support the bezel 4 and designing theinterior wall forming the concentric channel 5 with a conical surface 9to mate with the angle of the bezel 4, the edge of the bezel 4 may bespaced apart from the surface of the lens 6. Designing the concentricchannel 5 to support the bezel 4 fulfills the need of protecting theoptics of the lens 6 without the cost of an extra part (i.e., a spacer)and its handling in production.

As shown, for example in FIGS. 4A and 4B, wherein the indicatinginstrument 1 is a tachometer, the lens 6 is constructed with twoapertures, a pot shaft aperture 25 and a switch shaft aperture 31,through which the pot tube 66 and switch tube 68 extending from thelight plate 10 pass, respectively. In the embodiment depicted, pot tube66 and switch tube 68 extend no further than the exterior surface of thelens 6. A pot shaft extension 24 and a switch shaft extension 30 extendfrom a pot 42 and a switch 36, respectively, mounted on the PCB 70,through the pot tube 66 and switch tube 68, respectively, and extendabove the exterior surface of the lens 6 for actuation by a user. Thisdesign eliminates the need for additional, bulky interface structures275 externally attached to the indicating instrument 200 for usercontrol, as seen in prior art FIGS. 1A and 2A. It may be desirable toprovide user accessible controls on the face 3 of other types ofindicating instruments 1, and the techniques and configurationsdescribed herein with reference to the example tachometer are not meantto be limited to only that embodiment, but may be used to provide othertypes of control mechanisms to various embodiments of indicatinginstruments 1.

In the case of an indicating instrument 1 that is a tachometer, as inthis example embodiment, the pot 42 and switch 36 enable a user to setan RPM limit, at which point a shift indicator 26 is activated to signalto a driver that the chosen RPM has been reached. When the switch 36 isdepressed, current from the pot 42 (e.g., a potentiometer) is allowed topass to the meter movement 52 and sweep the pointer 16 to a desired RPMlimit. By varying the pot, and the current through it, a desired RPMlimit can be set. A clutch engagement 43, as seen in FIGS. 4B and 5, isused between the pot shaft extension 24 and the pot 42 to preventaccidental re-setting of an indicator trigger point. This inventionincorporates a hard, smooth clutch ball 46 between a clutch spring 44and a clutch base 48, all of which are contained in a cavity in the pot42. The clutch base 48 interfaces with the pot shaft extension 24, butthe clutch ball 46 and clutch spring 44 eliminate possible torquetransmittal to the pot 42 without depression of the pot shaft extension24, and thereby accidental resetting of the indicator 26 limit, at verylow cost. When the pot shaft extension 24 is depressed and rotated, theclutch base 48 pushes against the clutch ball 46 and depresses theclutch spring 44, whereby a dog 50 on the pot shaft extension 24 engagesa second dog 49 on the clutch base 48, thereby transmitting rotationfrom the pot shaft extension 24 to the pot 42 for setting the RPM limit.

Attached to the external ends of the pot shaft extension 24 and theswitch shaft extension 30 are a pot knob 22 and a switch knob 28,respectively, for ease of grasp by a user, allowing a user to manipulateand control the pot 42 and switch 36 functions. Prior art typically usessetscrews or holding clips for knob to shaft attachment. The presentinvention uses a novel knob to shaft attachment system that is shown indetail in FIGS. 9A–F in exemplary fashion with respect to the switchknob 28 and switch shaft extension 30, but equally applicable to the potknob 22 and pot shaft extension 24, or any other knob to shaftattachments in any application.

The switch knob 28, which may be made of rubber or other minimallycompressive elastic material, has axial keys 125 molded integrallywithin a cavity 126 within the shift knob 28. The switch shaft extension30 has mating axial keyways 124 molded in place. The switch shaftextension 30 also has a series of concentric barbs 122 that allow easyinstallation of the switch knob 28 on the switch shaft extension 30.While the installation of the shift knob 28 on the switch shaftextension 30 is easy, the interference between the walls of the shiftknob cavity 126 and the concentric barbs 122 on the switch shaftextension 30 prevent the easy removal of the shift knob 28. This knob toshaft system results in secure fixing of knobs on shafts at a lowmanufacturing cost.

Most indicating instruments with a sweeping pointer require a pointerstop. Prior art pointer stops 280, as seen in prior art FIG. 2A,typically employ a small metal post riveted to the dial in the vicinityof the zero mark to ensure that pointer 285 is at the zero position whenthere is no power or no signal condition. An embodiment of the presentinvention, as shown, for example, in FIGS. 3A, 4A, and 4B, utilizes ashift indicator 26, which may be a light emitting diode, and whichconnects to the PCB 70, extending through an aperture 27 in the lightplate 10, and protruding through the dial face 14. The shift indicator26 may be placed in an appropriate location near the zero mark on thedial face 14 to act as a stop for the pointer 16. This eliminates thecost of a metal post and its assembly to the dial face 14, whileproviding a valuable signaling feature to the user.

In the depicted embodiments, the pointer 16 may be constructed of moldedplastic. The pointer 16 is covered by a pointer cap 20, also of moldedplastic, which has a shaft 21 (FIG. 4B) that extends through the pointer16, the dial face 14, and the light plate 10 to engage the shaft 106extending from the meter movement 52. A detail of the pointer assemblyis shown in FIGS. 10A and 10B. The pointer cap 20 also conceals thepointer counterweight 18, which balances the pointer 16 as it movesthrough its sweep. A small hole 98 may be molded into the front of thepointer cap 20 and extend as a cavity through a length of the pointershaft 21. A rear cavity 99 in the opposite end of the pointer shaft 21also extends through a second length of the pointer shaft 21. In adeparture from the prior art, seen in FIG. 1A, in which the pointer 285is generally metallic with a through-hole for mounting the pointer 285on a shaft, the hole 98 in the pointer cap 20 and the rear cavity 99opposite it in the pointer shaft 21 are both blind holes in the presentinvention, but they come very close to meeting each other. A very thinmembrane 100 separates the pointer cap hole 98 from the rear cavity 99in the pointer shaft 21. As is known in the injection molding art,molding two blind holes is easier and less expensive than molding onethrough-hole.

Aside from being a subtle styling feature, the pointer cap hole 98 hasseveral useful purposes. First, the pointer cap hole 98 can be used witha special “pointer puller,” similar to a gear-puller, to remove thepointer 16 assembly from shaft 106 extending from the meter movement 52during production if removal and replacement of pointer 16 is needed.Use of a pointer-puller eliminates the possibility of excessive forcebeing placed on the thrust bearing of the meter movement 52 duringremoval of the pointer 16 from the shaft 106. From an injection moldingstandpoint, the pointer cap hole 98 in the center of the pointer cap 20reduces unsightly sink marks on the flat pointer cap 20 surface that canresult from the injection molding process.

In addition to the shift indicator 26 protruding from the face 3 of theindicating instrument 1, it may be desirable to provide a user with anexternal indicator to provide a greater degree of notification of theconditions measured by the indicating instrument 1. In the exampleembodiment of the tachometer described herein, an external indicator 77,shown for example in FIGS. 4A and 4B, is provided as a more visibleindicator of when the RPM threshold is reached. The external indicator77 may comprise a cylindrical housing 78, which screws into a threadedrear cap 80. The rear cap 80 may hold a lamp and socket assembly 82,which illuminates the external indicator 77, thereby providing thenotification to the user. A lens 86 may be held in the indicator housing78 by a retention ring 84, for example, a readily available rubberO-ring. Such a retention ring 84 is easy to install, inexpensive, andthe elasticity of the rubber compensates for tolerance variations andprovides rattle free operation.

A thin sheet of reflective material may be used for a reflector 87 toimprove the light output of external indicator 77. In one embodiment, adie-cut piece of white or reflective material is rolled into a conicalshape and placed in the housing. See FIGS. 13A and 13B. The depictedembodiment includes special die cut ends for the reflector 87, whereinthe tabbed end 102 slips into the slotted end 104. The die-cut tabbedand slotted ends provide for easier handling of the reflector 87 duringproduction and allow the reflector 87 to more easily stay in position.Once assembled, the conical form of the reflector 87 is securely heldtogether for easy installation.

As shown in FIGS. 4A, 4B, 15, and 19, the external indicator 77 may bealternately mounted to the housing 2 or positioned apart from the restof the indicating instrument 1. In the depicted embodiments, theexternal indicator 77 is attached to a mounting bracket 88. In theembodiment shown in FIGS. 4, 4A and 4B, the mounting bracket 88 issecured between the rear cap 80 and the external indicator housing 78.The mounting bracket 88 is further secured to the housing 2 of theindicating instrument 1 by mounting strap 90. The bracket foot 89 of themounting bracket 88 is restrained under mounting strap 90 that issecured around the circumference of the housing 2. The bracket foot 89may be arced to fit against the curvature of the housing 2. FIG. 19depicts an embodiment wherein the bracket foot 89 is reversed in itsattachment to both the external indicator and the housing 2. In thisembodiment, the external indicator 77 is seated further back withrespect to the indicating instrument 1, which could be useful dependingupon the space configurations of the environment in which the indicatinginstrument 1 is to be mounted.

The embodiment of FIG. 15 shows the mounting bracket 88 mounted at alocation remote from the indicating instrument 1. This embodiment allowsthe user to locate the external indicator 77 at a more optimal locationfor conspicuous notice by a user. The bracket foot 89 can likewise bereversed with respect to the external indicator 77 in this embodiment.The bracket foot 89 of the mounting bracket 88 may have one or moreapertures 127 (FIG. 4B) to allow for a simple attachment of the externalindicator 77 to a surface, such as by one or more screws 128 (FIG. 15)placed through the apertures 127 and secured into the surface.

A means of communication is needed in order to mount the externalindicator 77 remotely from the indicating instrument 1. In theembodiment depicted in FIG. 15, this communication is accomplished bylead wires 58 a–b connected to lead connectors 116 a–b (FIGS. 7B and 16)on the PCB 70 at a first end and connected to the external indicator 77at a second end. The lead wires 58 a–b exit the rear of the housing 2via an aperture 59, as shown in FIGS. 16 and 17. The aperture 59 isdepicted in FIG. 17 with a plug 60 that itself has an aperture 61allowing the lead wires 58 a–b to pass through the plug 60 and connectto the external indicator 77. The plug may be rubber or similarminimally compressive, elastic material. The plug 60 protects the leadwires 58 a–b from potential damage by the potentially sharp edges of thehousing 2 forming the aperture 59, and also provides a removable seal toaccess components inside the housing 2.

The aperture 59 in the depicted embodiment is a large opening allowingthe user to access several functional components of the indicatinginstrument 1. As discussed, the aperture 59 provides access forattachment of the lead wires 58 a–b to the lead connectors 116 a–b onthe PCB 70. Aperture 59 further allows access to the lamp socket 56 forremoval and replacement of the lamp 54, for instance if the lamp 54burns out. Aperture 59 may also provide user access to controls forspecific configurations of the indicating instrument 1. In the exampleembodiment of the tachometer, the aperture 59 provides access to a dipswitch 120 for selection of the number of cylinders of the vehicle toprovide appropriate timing information to the tachometer so that it canaccurately measure the rotations of the engine.

In the embodiment depicted in FIGS. 16 and 17, the indicating instrument1 further has a second aperture 39 in the rear wall of the housing 2.This aperture 39 provides a passage for signal wires 38 a–d from theirconnection points on the PCB 70 to connection points in the environmentfrom which they measure data. Signal wires 38 a–d may also be powertransmission wires for providing power to the indicating instrument ifneeded. In the case of the tachometer example, two of the signal wires,for example 38 a–b, are used to supply power to the tachometer. A thirdsignal wire, for example 38 c, is used to measure spark firings throughwhich the RPMs are measured. A fourth wire, for example 38 d, isconnected to the automobile's dash board illumination switch andsupplies power for illumination of the indicating instrument. Theaperture 39 is lined with a grommet 40 that itself has an aperture 37through which the signal wires 38 a–d pass. Similar to the plug 60, thegrommet 40 protects the signal wires 38 a–d from the potentially sharpedges of the housing 2 around the aperture 39. A conical surface asdepicted (FIG. 4B) on the insertion edge of the depicted grommet 40enables easy installation of the grommet 40 within the aperture 39 byaxial pressure.

In another embodiment of an indicating instrument 1, as shown in FIG.18, connections for lead wires 58 a–b and user setting interfaces may beaccessible at the surface of the housing 2 itself, without providingaccess to the PCB 70. The indicating instrument 1 of FIG. 18 is anembodiment wherein a selection switch 121 accessible through an aperturein the housing 2 allows the user to make a cylinder number selection forthe vehicle. Similarly, a protruding clip connector 117 provides aneasily accessible attachment means for the lead wires 58 a–b. Access toother user options and functionality connections for an indicatinginstrument 1 may similarly be provided.

The mounting strap 90 described previously and shown in FIGS. 4B, 14A,14B, 15, 18, and 19 may be a metal band formed to fit around thecircumference of the housing 2. The mounting strap 90 may have outturnedends 91 a–b that are held together around the housing 2 by a mountingbolt 95 and nut 96. A constant distance may be maintained betweenoutturned ends 91 a–b by a bolt sleeve 97 placed around the shaft of themounting bolt 95 between the outturned ends 91 a–b. Any otherconventional means for tightening or clamping the mounting strap 90around the housing 2, for example, a clamp, a buckle, and a compressivespring force inherent in the mounting strap 90, are contemplated withinthe scope of the invention. A strap pad 92, for example of rubber orsimilar minimally compressive, elastic material, designed to wrap aroundmetal strap 90 may additionally be placed on the mounting strap 90. Thewrap-around design of the strap pad 92 covers the potentially sharpedges of the mounting strap 90 providing better safety and appearance.Small ribs 133 may be formed on the bottom side of the strap pad 92, asshown in FIGS. 4B and 14B, to provide, for example, extra flexibilityfor good conformance of the mounting strap 90 to irregularities in thehousing 2 surface, a high friction interface between the housing 2 andmounting strap 90 preventing movement therebetween, and accommodationfor the extra thickness of the bracket foot 89 of the external indicator77 mounting bracket 88. The strap pad 92 may be optionally mounted onmounting strap 90 with the ribs 133 facing radially outwards as shownin, for example, FIGS. 14A and 19 for a different aesthetic appearance.

Once assembled, the mounting strap 90, strap pad 92, and mounting bolt95 assembly holds itself together around the housing 2. The assemblyalso allows for easy adjustment of radial position of the indicatinginstrument 1 within the mounting strap 90 by simply loosening themounting bolt 95 and rotating the indicating instrument 1. The designallows the indicating instrument 1 to be rotated 360° in relation tomounting strap 90 and mounting foot 94. This provides maximumflexibility and adaptability for installation of indicating instrument1.

The mounting foot 94 may be similarly attached to the mounting strap 90by the mounting bolt 95, and thereby pivot around the axis of themounting bolt 90. The design of the mounting foot 94 offers greatflexibility of positioning and use of the indicating instrument 1 asshown in FIGS. 20A–J. The mounting foot 94 may be attached to pointforward, as in FIGS. 20C–G and 20J, or to the rear, as in FIGS. 20A–Band 20H–I, allowing the indicating instrument 1 varying degrees of tiltin the mounted placement. Any particular angular position of theindicating instrument 1 with respect to the mounting foot 94 may be heldby simply tightening the mounting bolt 95 and nut 96. The mounting footmay similarly be rotated 360° with respect to the indicating instrumenthousing 2 by rotating the mounting strap 90 around the housing 2. Suchversatility in the mounting foot 94 allows the indicating instrument 1to be mounted in diverse positions and locations and be placed into manydifferent environments. For example, with a tachometer embodiment, byrotating the mounting foot 94 around the mounting bolt 95 and rotatingthe mounting foot 94 around the housing 2, the tachometer couldvariously be mounted in an automobile, for example, to the dashboard,the underside of the roof, a window column, a reinforcement post, or aroll bar.

Attachment of the mounting foot 94 to various surfaces may be achievedin a number of ways. The mounting foot may be provided with apertures132 a–b in its base for the reception of in attachment means, forexample screws. Mounting foot 94 may further be configured with an arch93 in its base so that the mounting foot 94 may better conform to acurved surface such as a window column, reinforcement post, or roll bar.The mounting foot 94 may further be provided slots 130 for theacceptance of a band for retaining the indicating instrument 1 against asurface. The band may be for example, a fabric or plastic strap, or evenan hose clamp, that may slip thorough the slots 130 and around amounting surface such as a reinforcement post or roll bar. The mountingfoot 94 may further be attached to a surface with an adhesive placedbetween the mounting foot 94 and the surface.

Although various embodiments of this invention have been described abovewith a certain degree of particularity, or with reference to one or moreindividual embodiments, those skilled in the art could make numerousalterations to the disclosed embodiments without departing from thespirit or scope of this invention. It is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative only of particularembodiments and not limiting. Changes in detail or structure may be madewithout departing from the basic elements of the invention as defined inthe following claims.

1. A lens comprising a first face; the first face comprising a channelaround a peripheral edge of the lens; and a second face; the second facecomprising a projection around the peripheral edge of the lens; whereinwhen at least two lenses are stacked upon each other, the projection ofthe second face of a first lens engages the channel of the first face ofa second lens, preventing relative movement between the first lens andthe second lens and maintaining a gap between the second face of thefirst lens and the first face of the second lens.
 2. The lens asdescribed in claim 1, wherein at least a portion of the first facecomprises an optical surface; and the channel further comprises: a firstwall; and a second wall; wherein the first wall and the second wall formthe bounds of the channel; and at least one of the first wall and thesecond wall projects above the optical surface; wherein the opticalsurface of the first face is protected from scratches and other damagewhen the lens is set upon a generally flat surface.
 3. The lens asdescribed in claim 2, wherein the second wall is bounded by the firstwall; and an interior side of the second wall forms a beveled edgeangled to support a bezel and to separate a front edge of the bezel fromthe optical surface of the first face.
 4. The lens as described in claim1, wherein at least a portion of the second face comprises an opticalsurface; and the projection projects above the optical surface; whereinthe optical surface of the second face is protected from scratches andother damage when the lens is set upon a generally flat surface.
 5. Thelens as described in claim 1, wherein the lens is circular; the channelis concentric with the center of the lens; and the projection isconcentric with the center of the lens.
 6. The lens as described inclaim 1, wherein the channel is adapted to support a bezel and toseparate an edge of the bezel from the optical surface of the firstface.
 7. The lens as described in claim 1, wherein the second wall isbounded by the first wall; the first face and the second face compriseopposing sides of a lens body; and at least a portion of the first wallextends beyond a peripheral edge of the lens body.
 8. A lens comprisinga first face; the first face comprising a first engagement structureextending above the first face and around a peripheral edge of the lens;and a second face; the second face comprising a second engagementstructure extending above the second face and around the peripheral edgeof the lens; wherein when at least two lenses are stacked upon eachother, the second engagement structure of the second face of a firstlens engages the first engagement structure of the first face of asecond lens, preventing relative movement between the first lens and thesecond lens and maintaining a gap between the second face of the firstlens and the first face of the second lens.